Communication device and communication method

ABSTRACT

Disclosed are a wireless communication base station device, a wireless communication terminal device, and a wireless communication method with which the amount of signaling is reduced while maintaining a high scheduling gain. A judgment unit ( 117 ) stores in advance a correspondence between the number of code words and the number of clusters to reduce the maximum value for the number of clusters allocated to each terminal as the number of code words increases, and thus determines the maximum value for the number of clusters based on the number of code words acquired. Based on the number of code words for a transmission signal from a terminal, an estimated value for the reception quality that is output by an estimation unit ( 109 ), and the maximum value for the number of clusters that is output by the judgment unit ( 117 ), a scheduling unit ( 118 ) schedules the allocation of the transmission signal transmitted by each terminal to a transmission band frequency (frequency resource) so as not to exceed the maximum value for the number of clusters.

TECHNICAL FIELD

The present invention relates to a communication apparatus and acommunication method.

BACKGROUND ART

In uplink of 3rd generation partnership project long term evolution(3GPP LTE), consecutive bands are allocated to individual terminals. Ineach band, data signals and pilot signals are time-multiplexed andtransmitted.

Notification information for each terminal includes transmission bandinformation and control information. Here, the transmission bandinformation includes start and end resource block (RB) numbers of anallocation band (a minimum bandwidth is set to 1 RB) determined from asystem bandwidth N_(RB). The number of notification bits of the startand end RB numbers is expressed by following equation 1.

$\begin{matrix}{\left( {{Equation}\mspace{14mu} 1} \right)\mspace{619mu}} & \; \\{\left\lceil {\log_{2}{\,\left( {}_{N_{RB} + 1}C_{2} \right)}} \right\rceil = \left\lceil {\log_{2}\frac{\left( {N_{RB} + 1} \right)\left( N_{RB} \right)}{2!}} \right\rceil} & \lbrack 1\rbrack\end{matrix}$

Further, the control information includes 5-bit modulation and codingscheme (MCS) information, 2-bit TCP command information, 1-bit new dataindicator (NDI) information, 3-bit cyclic shift information, and thelike. That is, in this example, the number of bits to be required fornotification of control information is 11.

In Non-Patent Literature 1, in addition to consecutive band allocationin uplink of LTE-Advanced which is a developed version of 3GPP LTE,allocating non-consecutive bands (non-consecutive allocation) isdiscussed (see FIG.1). Flexible frequency scheduling is possible thanksto allocating non-consecutive bands. Further, in the non-consecutiveallocation, allocated consecutive bands are called a cluster.

Meanwhile, in Non-Patent Literature 2, multiple input multiple output(MIMO) transmission of data signals is discussed. In the MIMOtransmission in LTE, transmission control (MCS control and the like) canbe performed in units of codeword, and flexible space scheduling ispossible. Further, a codeword represents a block, which is aretransmission unit of hybrid automatic repeat and request (HARQ).

When the non-consecutive allocation and the MIMO transmission areapplied, a schedule gain based on space scheduling or frequencyscheduling may increase.

CITATION LIST Non-Patent Literature

-   NPL 1-   R1-081752, “Proposals on PHY related aspects in LTE Advanced”, 3GPP    TSG RANI #53, Kansas City, Mo., USA, 5-9 May, 2008-   NPL 2-   R1-090308, “Investigation on Uplink Radio Access Scheme for    LTE-Advanced”, 3GPP TSG RANI #55bis, Ljubljana, Slovenia, 12-16    Jan., 2009

SUMMARY OF INVENTION Technical Problem

In the non-consecutive allocation, when the system bandwidth is denotedby N_(RB) and the number of clusters is denoted by Ncluster, the numberof bits of an allocated band is expressed by the following Equation 2.

$\begin{matrix}{\left( {{Equation}\mspace{14mu} 2} \right)\mspace{619mu}} & \; \\{\left\lceil {\log_{2}\left( {}_{N_{RB} + 1}C_{2N_{cluster}} \right)} \right\rceil = \left\lceil {\log_{2}\left( \frac{\left( {N_{RB} + 1} \right)\left( N_{RB} \right)\mspace{14mu} \ldots \mspace{14mu} \left( {N_{RB} + 1 - {2N_{cluster}} + 1} \right)}{\left( {2N_{cluster}} \right)!} \right)} \right\rceil} & \lbrack 2\rbrack\end{matrix}$

In the MIMO transmission, 11-bit control information is necessary foreach codeword.

Accordingly, as the number of codewords or the number of clustersincreases, the amount of signaling to notify in a downlink controlinformation (DCI) format increases (see FIGS. 2 and 3). The DCI formatis a format for transmitting resource allocation information and controlinformation.

For example, as shown in FIG. 3, if the number of codewords increases,the control information increases, and if the number of clustersincreases, the resource allocation information increases. Further, asshown in FIG. 2 (on the assumption that the system bandwidth is 100RBs), when the number of codewords is 1 and the number of clusters is 1,24 bits are necessary. However, when the number of codewords is 2 andthe number of clusters is 2, 46 bits are necessary.

It is therefore an object of the present invention to provide acommunication apparatus and a communication method which reduce asignaling amount while securing a high scheduling gain.

Solution to Problem

A communication apparatus according to the present invention includes: adetermination section that determines a maximum value of the number ofclusters such that the maximum value of the number of clusters toallocate to another communication apparatus is reduced as the number ofcodewords of a transmission signal to allocate to the othercommunication apparatus increases; and a scheduling section thatallocates a band of a transmission signal to be transmitted by the othercommunication apparatus based on the determined maximum value of thenumber of clusters.

A communication apparatus according to the present invention includes: aband identifying section that determines that a maximum value of thenumber of clusters to allocate to that communication apparatus issmaller as the number of codewords allocated to the communicationapparatus is larger, and identifies a transmission band allocated to thecommunication apparatus, based on the number of codewords and themaximum value of the number of clusters; and a transmission section thattransmits a data signal using the identified transmission band.

A communication method according to the present invention includes:determining a maximum value of the number of clusters such that themaximum value of the number of clusters to allocate to anothercommunication apparatus is reduced as the number of codewords of atransmission signal to allocate to the other communication apparatusincreases; and performing allocation of a band of a transmission signalto be transmitted by the other communication apparatus, based on thedetermined maximum value of the number of clusters.

Advantageous Effects of Invention

According to the present invention, it is possible to reduce a signalingamount while securing a high scheduling gain.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a view illustrating states of consecutive band allocation andnon-consecutive band allocation;

FIG. 2 is a view illustrating signaling amounts in a case of applyingMIMO transmission and the non-consecutive band allocation;

FIG. 3 is a view illustrating changes of the amount of signaling tonotify in a DCI format in a case where the number of codewords or thenumber of clusters increases;

FIG. 4 is a block diagram illustrating a configuration of a base stationaccording to Embodiment 1 of the present invention;

FIG. 5 is a view illustrating a state in which the maximum value of thenumber of clusters to allocate to each terminal is reduced as the numberof codewords increases;

FIG. 6 is a view illustrating a state in which allocation controlinformation is generated;

FIG. 7 is a block diagram illustrating a configuration of a terminalaccording to Embodiment 1 of the present invention;

FIG. 8 is a view illustrating a state in which the maximum value of thenumber of clusters to allocate to each terminal is reduced as the numberof codewords increases;

FIG. 9 is a view illustrating a state in which selectable start and endRBs vary according to the number of codewords;

FIG. 10A is a view illustrating a signaling amount of start and end RBs;

FIG. 10B is a view illustrating a signaling amount of start and end RBs;

FIG. 11A is a view illustrating RBs selectable as an end RB according tothe number of codewords;

FIG. 11B is a view illustrating RBs selectable as the end RB accordingto the number of codewords;

FIG. 12 is a view illustrating a state in which the maximum value of thenumber of clusters to allocate to each terminal is reduced as the numberof layers or the number of streams increases; and

FIG. 13 is a view illustrating a state in which selectable start and endRBs vary according to the number of layers or the number of streams.

DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments of the present invention will be described indetail with reference to the drawings. In the embodiments, componentshaving the identical function are denoted by the same reference symbols,and a redundant description will not be repeated.

Embodiment 1

FIG. 4 is a block diagram illustrating a configuration of base station100 according to Embodiment 1 of the present invention. In this figure,encoding section 101 acquires transmission data (downlink data), aresponse signal (an ACK signal or a NACK signal) input from errordetection section 116 to be described below, resource allocationinformation of each terminal input from scheduling section 118 to bedescribed below, control information representing an MCS, and the like.The response signal, the resource allocation information, and thecontrol information constitute allocation control information. Encodingsection 101 encodes the transmission data and the allocation controlinformation, and outputs the encoded data to modulation section 102.

Modulation section 102 modulates the encoded data output from encodingsection 101, and outputs the modulated signal to RF transmitting section103.

RF transmitting section 103 performs predetermined transmissionprocesses, such as D/A conversion, up-conversion, and amplification, onthe modulated signal output from modulation section 102, and wirelesslytransmits the signal having been subjected to the transmission processesto each terminal through one or more antennas 104.

RF receiving section 105 performs predetermined reception processes,such as down-conversion and A/D conversion, on a signal received fromeach terminal through antennas 104, and outputs the signal having beensubjected to the reception processes to separation section 106.

Separation section 106 separates the signal output from RF receivingsection 105 into a pilot signal and a data signal, and outputs the pilotsignal and the data signal to discrete Fourier transform (DFT) section107 and DFT section 110, respectively.

DFT section 107 section performs a DFT process on the pilot signaloutput from separation section 106 thereby to perform signal conversionfrom a time domain to a frequency domain. DFT section 107 outputs theconverted pilot signal in the frequency domain to demapping section 108.

Demapping section 108 extracts a partial pilot signal corresponding to atransmission band of each terminal from the pilot signal in thefrequency domain output from DFT section 107, and outputs each extractedpilot signal to estimation section 109.

Estimation section 109 estimates the frequency variation (that is,channel frequency response) and reception quality of a channel, based onthe pilot signal output from demapping section 108. Estimation section109 outputs an estimated value of channel frequency variation to signalseparation section 112, and outputs an estimated value of receptionquality to scheduling section 118.

Meanwhile, DFT section 110 performs a DFT process on the data signaloutput from separation section 106, thereby performing signal conversionfrom a time domain to a frequency domain. DFT section 110 outputs theconverted data signal in the frequency domain to demapping section 111.

Demapping section 111 extracts a partial data signal corresponding tothe transmission band of each terminal from the data signal in thefrequency domain output from DFT section 110, and outputs each extracteddata signal to signal separation section 112.

Signal separation section 112 weights and synthesizes the data signalsoutput from demapping section 111 by using the estimated value ofchannel frequency variation output from estimation section 109, therebyseparating the data signal so as to correspond to each layer. Theseparated data signal is output to Inverse Fast Fourier Transform (IFFT)section 113.

IFFT section 113 performs an IFFT process on the data signal output fromsignal separation section 112, and outputs the signal having beensubjected to the IFFT process to demodulation section 114.

Demodulation section 114 performs a demodulation process on the signaloutput from IFFT section 113, and outputs the demodulated signal todecoding section 115.

Decoding section 115 performs a decoding process on the signal outputfrom demodulation section 114, and outputs the decoded signal (decodedbit sequence) to error detection section 116.

Error detection section 116 performs error detection on the decoded bitsequence output from decoding section 115. For example, error detectionsection 116 performs error detection using a CRC check. When an error isdetected from the decoded bits as a result of error detection, errordetection section 116 generates a NACK signal as a response signal, andwhen no error is detected from the decoded bits, error detection section116 generates an ACK signal as the response signal. The generatedresponse signal is output to encoding section 101. In the case wherethere is no error in the decoded bits, the data signal is output asreception data.

Determination section 117 acquires the number of codewords of atransmission signal to allocate to the terminal from a control sectionor the like (not shown), and controls the maximum value of the number ofclusters to allocate to each terminal according to the number ofcodewords. That is, as the number of codewords increases, the maximumvalue of the number of clusters to allocate to each terminal is reduced.Specifically, determination section 117 stores correspondence betweenthe numbers of codewords and the numbers of clusters as shown in FIG. 5in advance, and determines the maximum value of the number of clustersfrom the obtained number of codewords. The determined maximum value ofthe number of clusters is output to scheduling section 118. In FIG. 5,shaded portions indicate unused portions.

Scheduling section 118 schedules allocation of a transmission band(frequency resource) of a transmission signal transmitted by eachterminal so as not to exceed the maximum value of the number ofclusters, based on the number of codewords of the transmission signal toallocate to the terminal, which is acquired from the control section orthe like (not shown), the estimated value of reception quality outputfrom estimation section 109, and the maximum value of the number ofclusters output from determination section 117. The allocation controlinformation (for example, the resource allocation information and thecontrol information) representing the scheduling result is output toencoding section 101.

The allocation control information representing the scheduling resultmay be generated in correspondence with the maximum value of the numberof clusters and the number of codewords. For example, in a case wherethe size of a DCI format varies according to the maximum value of thenumber of clusters and the number of codewords as shown in FIG. 2, andthe number of clusters to allocate to a resource is I with respect tothe maximum value of the number of clusters of 2 as shown in FIG. 6, asignaling area for the second cluster is filled with padding bits. Here,the padding bits refer to bits used for filling an available area of theDCI format. Further, the size of the DCI format may be unified to thelargest size regardless of the maximum value of the number of clustersand the number of codewords, and the padding bits may fill in an areaother than the signaling areas used for the resource allocationinformation and the control information. In this case, padding bits toequal in number the difference between the size of the DCI format andthe size used for signaling are necessary.

FIG. 7 is a block diagram illustrating a configuration of terminal 200according to Embodiment 1 of the present invention. In this figure, RFreceiving section 202 performs predetermined reception processes, suchas down-conversion and AID conversion, on a signal received from thebase station through antenna 201, and outputs the signal having beensubjected to the reception processes to demodulation section 203.

Demodulation section 203 performs an equalization process and ademodulation process on the signal output from the RF receiving section202, and outputs the processed signal to decoding section 204.

Decoding section 204 performs a decoding process on the signal outputfrom demodulation section 203, and extracts reception data andallocation control information. The allocation control informationincludes the response signal (the ACK signal or the NACK signal), theresource allocation information, the control information, andinformation on the number of codewords. Decoding section 204 outputs theresource allocation information, the control information, and theinformation on the number of codewords out of the extracted allocationcontrol information to band identifying section 205.

Band identifying section 205 determines the maximum value of the numberof clusters to allocate to terminal 200, based on the number ofcodewords output from decoding section 204. That is, it is determinedthat the larger the number of codewords, the smaller the maximum valueof the number of clusters to allocate to terminal 200. Specifically,band identifying section 205 stores the correspondence between thenumber of codewords and the number of clusters as shown in FIG. 5 inadvance, determines the maximum value of the number of clusters based onthe information on the number of codewords output from decoding section204, extracts the resource allocation information and the controlinformation for terminal 200 by using the maximum value of the number ofclusters and the number of codewords, and identifies a transmission bandallocated to terminal 200. For example, since the size of the DCI formatvaries according to the maximum value of the number of clusters and thenumber of codewords, band identifying section 205 determines the maximumvalue of the number of clusters based on the number of codewords input,and learns the size and structure of the DCI format as shown in FIG. 6,from the maximum value of the number of clusters and the number ofcodewords. Then, band identifying section 205 extracts the resourceallocation information and the control information for terminal 200. Ina case where the number of allocated clusters is smaller than themaximum value of the number of clusters, since the padding bits fill apartial signaling area of the resource allocation information, it ispossible to learn the number of clusters.

Transmission data made of one or more codewords is divided and is inputto CRC section 206. CRC section 206 performs CRC encoding on the inputtransmission data so as to generate CRC-encoded data, and outputs thegenerated CRC-encoded data to encoding section 207.

Encoding section 207 encodes the CRC-encoded data output from CRCsection 206, and outputs the encoded data to modulation section 208.

Modulation section 208 modulates the encoded data output from encodingsection 207, and outputs the modulated data signal to allocation section209.

Allocation section 209 allocates the data signal output from modulationsection 208 to a frequency resource (RB) based on the band informationoutput from band identifying section 205. The data signal to allocate tothe RB is output to multiplexing section 210.

Multiplexing section 210 time-multiplexes the pilot signal and the datasignal output from allocation section 209, and outputs the multiplexedsignal to transmission power weight control section 211.

Transmission power weight control section 211 multiplies eachmultiplexed signal output from multiplexing section 210 by atransmission power weight determined based on the channel informationinput from the control section or the like (not shown), and outputs thegenerated signal to RF transmitting section 212.

RF transmitting section 212 performs predetermined transmissionprocesses, such as D/A conversion, up-conversion, and amplification, onthe multiplexed signal output from multiplexing section 210, andwirelessly transmits the signal having been subjected to thetransmission processes to the base station through antennas 201.

Next, the above-described correspondence between the number of codewordsand the number of clusters stored in determination section 117 of thebase station and band identifying section 205 of the terminal as shownin FIG. 5 will be described.

The number of codewords and the number of clusters have thecorrespondence relationship in which the maximum value of the number ofclusters to allocate to each terminal is reduced as the number ofcodewords increases. For example, when the number of codewords is 1, themaximum value of the number of clusters is set to 4, and when the numberof codewords is 2, the maximum value of the number of clusters is set to3, and when the number of codewords is 4, the maximum value of thenumber of clusters is set to 1.

In this case, when the number of codewords is 1 and the maximum value ofthe number of clusters is 4, since the number of clusters is larger, itis possible to secure a scheduling gain by a frequency scheduling gain.Meanwhile, when the number of codewords is 4 and the maximum value ofthe number of clusters is 1, since the number of codewords is larger, itis possible to secure the scheduling gain by a space scheduling gain.Further, since a case where the number of codewords is 4 and the numberof clusters is 4 or the like does not occur, it is possible to reducethe amount of signaling. Moreover, in a case where the number ofcodewords is large and the number of clusters is large, since thescheduling gain approaches the saturation, improvement effect by thescheduling gain from a case where there is only the space schedulinggain or the frequency scheduling gain is not great.

As described above, according to Embodiment 1, the maximum value of thenumber of clusters to allocate to each terminal is controlled accordingto the number of codewords of the transmission signal to allocate to theterminal. Therefore, it is possible to reduce the amount of signalingwhile securing a high scheduling gain. Further, by limiting that both ofthe number of clusters and the number of codewords become large.Therefore, it is possible to reduce the amount of signaling.

The maximum value of the number of clusters according to each number ofcodewords may be set such that the amount of signaling does not exceed areference number of bits but is closest to the reference number of bits.For example, a case where the reference number of bits is set to 63which is the number of bits when the number of codewords is 1 and thenumber of clusters is 4 is shown in FIG. 8. In this case, even when thenumber of codewords is 2, 3, or 4, the maximum value of the number ofclusters is determined such that the number of notification bits doesnot exceed 63. For example, assuming that the number of codewords is 2,when the number of clusters is 3, since the number of notification bitsis 67, exceeding 63 which is the reference number of bits, the maximumvalue of the number of clusters is set to 2. Even when the number ofcodewords is 3 or 4, the maximum value of the number of clusters isdetermined similarly. In FIG. 8, shaded portions show unused portions.

In this way, it is possible to use DCI formats having the same sizeregardless of the number of codewords while suppressing the number ofpadding bits.

In the present embodiment, a usable range may be limited to only a rangein which the product of the number of codewords and the number ofclusters is equal to or less than a predetermined value.

In the present embodiment, it has been described that the number ofclusters varies according to the number of codewords. However, thenumber of clusters may vary according to the number of layers or thenumber of streams. For example, in a case where the number of codewordscorresponds one-to-one with the number of layers or the number ofstreams, the number of codewords may be replaced with the number oflayers or the number of streams. In a case where the number of codewordscorresponds one-to-many with the number of layers or the number ofstreams, the number of codewords may be replaced with the number oflayers or the number of streams. For example, in a case of changing thecontrol information (cyclic shift and the like) in each layer or eachstream even when the number of codewords is 1, the amount of controlinformation increases as the number of layers or the number of streamsincreases. Accordingly, the number of clusters changes according to thenumber of layers or the number of streams.

Further, in the present embodiment, it has been described that thenumber of clusters varies according to the number of codewords. However,the correspondence relationship between these may be reversed such thatthe number of codewords varies according to the number of clusters.Thereby, it is possible to reduce the amount of signaling while securinga high scheduling gain. Further, as described above, the number ofcodewords for each number of clusters may be set such that the amount ofsignaling does not exceed the reference number of bits but is closest tothe reference number of bits. For example, in a case where the referencenumber of bits is set to 63 which is the number of bits when the numberof clusters is 4 and the number of codewords is 1, the number ofcodewords is determined as shown in FIG. 8. In this case, even when thenumber of clusters is 3, 2, or 1, the number of codewords is determinedsuch that the number of notification bits does not exceed 63. When thenumber of clusters is 3, if the number of codewords is 2, the number ofnotification bits is 67, exceeding the reference number of bits.Accordingly, the maximum number of codewords is set to 1. Even when thenumber of clusters is 3 or 4, similarly, the number of codewords is setto 3 or 4 such that the number of notification bits does not exceed thereference number of bits. Therefore, it is possible to keep the amountof signaling constant regardless of the number of clusters.

Furthermore, in the present embodiment, when the number of codewords is2 or more, the number of clusters may be fixed to 1.

Embodiment 2

In Embodiment 2 of the present invention, an RB available as a startposition of clusters to allocate to a terminal is referred to as a startRB, and an RB available as an end position of the clusters is referredto as an end RB. The start RB and the end RB, or the start RB, or theend RB is collectively referred to as start/end RBs.

A configuration of a base station according to Embodiment 2 of thepresent invention is the same as the configuration of Embodiment 1 shownin FIG. 4, except for some functions, and thus only the differentfunctions will be described with reference to FIG. 4.

Determination section 117 receives the number of codewords to allocateto each terminal from the control section or the like (not shown), andcontrols available start/end RBs of clusters to allocate to eachterminal, according to the number of codewords. That is, the availablestart/end RBs of the clusters to allocate to each terminal are reducedas the number of codewords increases. Determination section 117determines the available start/end RBs of the clusters to allocate toeach terminal, based on the input number of codewords, and outputs thedetermined start/end RBs to scheduling section 118. For example, whenthe number of codewords is 1, each RB can be selected as the start/endRB. In contrast, when the number of codewords is 2, second, fourth,sixth, . . . RBs can be selected as the start/end RB.

Scheduling section 118 allocates the transmission band (frequencyresource) of the transmission signal transmitted by each terminal, basedon the number of codewords of the transmission signal to allocate to theterminal which is acquired from the control section or the like (notshown), the estimated value of reception quality output from estimationsection 109, and the start/end RB output from determination section 117.The allocation control information (for example, the resource allocationinformation and the control information) representing the schedulingresult is output to encoding section 101.

The allocation control information representing the scheduling resultmay be generated in association with the number of codewords and thestart/end RB. For example, as shown in FIG. 9, the selectable start/endRBs may vary according to the number of codewords, and the resourceallocation information may be generated in units of one RB when thenumber of codewords is 1, and the resource allocation information may begenerated in units of two RBs when the number of codewords is 2.

A configuration of a terminal according to Embodiment 2 of the presentinvention is the same as the configuration of Embodiment 1 shown in FIG.7, except for some functions, and thus only the different functions willbe described with reference to FIG. 7.

Band identifying section 205 determines the available start/end RBs ofthe clusters to allocate to terminal 200, according to the number ofcodewords output from decoding section 204. That is, band identifyingsection 205 determines a smaller number of available start/end RBs ofthe clusters to allocate to each terminal, with respect to a largernumber of codewords. Specifically, band identifying section 205 storesthe correspondence between the number of codewords and the availablestart/end RBs of the clusters in advance, and determines the availablestart/end RB of the clusters based on the information on the number ofcodewords output from decoding section 204.

Band identifying section 205 determines the start/end RB of thetransmission band allocated to terminal 200 from the available start/endRBs by using the control information output from decoding section 204.For example, band identifying section 205 judges that the resourceallocation information is in units of I RB when the number of codewordsis 1 and judges that the resource allocation information is in units of2 RBs when the number of codewords is 2, and determines the start/end RBof the transmission band.

A signaling amount of the start/end RB in a case of reducing theavailable start/end RBs of the clusters to allocate to each terminal asthe number of codewords increases will be described with reference toFIG. 10. FIG. 10 is based upon a premise that the system bandwidth is 6RBs, FIG. 10A shows a case of selecting the start/end RB in units of 1RB, and FIG. 10B shows a case of selecting the start/end RB in units of2 RBs.

As shown in FIG. 10A, in the case of selecting the start/end RB in unitsof 1 RB, the start/end RB is selected from 7 RBs (3 bits) of 0th to 6thRBs in FIG. 10A. However, as shown in FIG. 10B, in the case of selectingthe start/end RB in units of 2 RBs, the start/end RB is selected from 4RBs (2 bits) of 0th to 3rd RBs in FIG. 10B. In this way, the availableRBs of the clusters are reduced such that the amount of signaling of thestart/end RB to notify to the terminal changes from 3 bits to 2 bits.Therefore, it is possible to reduce the amount of signaling.

In a case where the space scheduling gain is high and the number ofcodewords is large, the start/end RBs according to the number ofclusters to allocate to each terminal is reduced, whereby it is possibleto reduce the amount of signaling while securing the scheduling gain.

As described above, according to Embodiment 2, the available start/endRBs of the clusters to allocate to each terminal are controlledaccording to the number of codewords of the transmission signal toallocate to the terminal. Therefore, it is possible to reduce the amountof signaling while securing a high scheduling gain.

Embodiment 2 and Embodiment 1 may be combined. For example, although ithas been described that the number of codewords may vary according tothe number of clusters, the codewords may be replaced with the availablestart/end RBs of the clusters to allocate to each terminal. That is, acorrespondence relationship in which if the number of clusters is 1, 2,3, or 4, the available start/end RBs of the clusters to allocate to eachterminal are in units of 1 RB, 2 RBs, 3 RBs, or 4 RBs may be defined. Asdescribed in Embodiment 1, the start/end RBs according to the number ofclusters may be selected such that the amount of signaling does notexceed the reference number of bits but is closest to the referencenumber of bits. For example, when the start/end RBs are in units of 1RB, the number of clusters is limited to 1, and when the start/end RBsare in units of 2 RBs, the number of clusters is limited to 2. Also,when the start/end RBs are in units of 3 RBs and 4 RBs, the number ofclusters is limited to 3 and 4, respectively. Also, when the number ofclusters is 1, the start/end RBs are limited to units of 1 RB, and whenthe number of clusters is 2, the start/end RBs are limited to units of 2RBs. Further, when the number of clusters is 3 and 4, the start/end RBsare limited to units of 3 RBs and 4 RBs, respectively. By using this, itis possible to adjust the number of clusters and the start/end RBs andto limit the amount of signaling to a number of bits which does notexceed the reference number of bits as described in Embodiment 1.

Embodiment 3

In Embodiment 3 of the present invention, an RB available as a startposition of clusters to allocate to a terminal is referred to as a startRB, and an RB available as an end position is referred to as an end RB.

A configuration of a base station according to Embodiment 3 of thepresent invention is the same as the configuration of Embodiment 1 shownin FIG. 4, except for some functions, and thus only the differentfunctions will be described with reference to FIG. 4.

Determination section 117 receives the number of codewords to allocateto each terminal from the control section or the like (not shown), andcontrols the available start RBs and end RBs of the clusters to allocateto the terminal, according to the number of codewords. Specifically, asthe number of codewords increases, the available end RBs of the clustersto allocate to each terminal are selected in a range separated from thestart RB. Determination section 117 determines the available start RBsand end RBs of the clusters to allocate to each terminal, based on theinput number of codewords, and outputs the determined start RBs and endRBs to scheduling section 118. For example, with respect to theavailable end RBs, only RBs separated from the available start RB by apredetermined number of RBs or more are set as the available end RBs forthe end RB.

Scheduling section 118 allocates the transmission band (frequencyresource) of the transmission signal transmitted by each terminal, basedon the number of codewords of the transmission signal to allocate to theterminal, the number of codewords being obtained from the controlsection or the like (not shown), the estimated value of receptionquality output from estimation section 109, and the start RBs and theend RBs output from determination section 117. The allocation controlinformation (for example, the resource allocation information and thecontrol information) representing the scheduling result is output toencoding section 101.

A configuration of a terminal according to Embodiment 2 of the presentinvention is the same as the configuration of Embodiment 1 shown in FIG.7, except for some functions, and thus only the different functions willbe described with reference to FIG. 7.

Band identifying section 205 controls the available start RBs and endRBs of the clusters to allocate to terminal 200, according to the numberof codewords output from decoding section 204. Specifically, as thenumber of codewords increases, the available end RBs of the clusters toallocate to terminal 200 are selected in a range separated from thestart RB. That is, band identifying section 205 stores thecorrespondence between the range separated from the start RB for theavailable end RBs of the clusters and the number of codewords inadvance, and determines the available start RBs and end RBs of theclusters based on the information on the number of codewords output fromdecoding section 204. Band identifying section 205 determines the startRB and end RB of the transmission band allocated to terminal 200 fromthe available start RBs and end RBs by using the control informationoutput from decoding section 204. For example, when the number ofcodewords is 1, the end RB is selectable from RBs separated from thestart RB by 1 RB or more (see FIG. 11A), and when the number ofcodewords is 2, the end RB is selectable only from RBs that are 2 RBs ormore distant from the start RB, and when the number of codewords is 3,the end RB is selectable only from RBs 3 RBs or more distant from thestart RB (see FIG. 11B).

As described above, according to Embodiment 3 of the present invention,the available end RBs of the clusters to allocate to each terminal areselected in a range separated from the start RB, according to the numberof codewords of the transmission signal to allocate to the terminal.Therefore, it is possible to reduce the amount of signaling whilesecuring a high scheduling gain.

In the present embodiment, it has been described that the number ofclusters or the start/end RBs of the clusters are restricted accordingto the number of codewords. However, the number of clusters or thestart/end RBs of the clusters may be restricted according to the numberof layers or the number of streams. For example, in a case where thenumber of codewords corresponds one-to-one with the number of layers orthe number of streams, the number of codewords may be replaced with thenumber of layers or the number of streams. Further, even in a case wherethe number of codewords corresponds one-to-many with the number oflayers, the number of codewords can be replaced with the number oflayers or the number of streams. For example, even when the number ofcodewords is 1, in a case where control information (cyclic shift andthe like) changes in each layer or each stream, the amount of controlinformation increases as the number of layers or the number of streamsincreases. Accordingly, the number of clusters is restricted accordingto the number of layers or the number of streams (FIG. 12). Also, sincethe amount of control information increases as the number of layers orthe number of streams increases, the start/end RBs of the clusters arerestricted according to the number of layers or the number of streams(FIG. 13).

In each above-mentioned embodiment, the number of bits for the controlinformation and the allocation is not limited to the number of bitsshown in tables.

Each above-mentioned embodiment has been described on the premise ofuplink. However, the present invention may be applied to downlink. Forexample, in Embodiment 3, it has been described that “the number ofuplink clusters is controlled according to the number of uplinkcodewords” and “the start/end RBs of uplink clusters are restrictedaccording to the number of uplink codewords.” However, “the number ofdownlink clusters may be controlled according to the number of downlinkcodewords,” and “the start/end RBs of downlink clusters may berestricted according to the number of downlink codewords.”

Further, in each above-mentioned embodiment, it has been described thatthe number of clusters or the start/end RBs of the clusters arecontrolled according to the number of codewords. However, the control isnot limited to the number of codewords. The number of codewords may bereplaced with a predetermined block constituting a data signal. Forexample, the number of codewords may be replaced with the number oflayers to which the data signal is allocated, and may be replaced withthe number of resource blocks (RBs) to which the data signal isallocated or the number of consecutive bands (the number of clusters) towhich the data signal is allocated.

Each above-mentioned embodiment has been described on the premise thatthe base station controls the number of clusters or the start/end RBs ofuplink clusters according to the number of uplink codewords in the basestation, and, according to this, the terminal performs uplinktransmission. However, the present invention is not limited thereto. Theterminal may determine the number of codewords or the start/end RBs ofuplink clusters by itself and control the number of clusters or thestart/end RBs of uplink clusters based on the same method as the presentinvention, and, according to this, the base station may perform uplinkreception. Further, the base station may determine the number ofdownlink codewords and control the number of clusters or the start/endRBs of downlink clusters based on the same control method as the presentinvention, and, according to this, the terminal may perform downlinkreception.

Also, although cases have been described with the above embodiment asexamples where the present invention is configured by hardware, thepresent invention can also be realized by software.

Each function block employed in the description of each of theaforementioned embodiments may typically be implemented as an LSIconstituted by an integrated circuit. These may be individual chips orpartially or totally contained on a single chip. “LSI” is adopted herebut this may also be referred to as “IC,” “system LSI,” “super LSI,” or“ultra LSI” depending on differing extents of integration.

Further, the method of circuit integration is not limited to LSI's, andimplementation using dedicated circuitry or general purpose processorsis also possible. After LSI manufacture, utilization of a programmableFPGA (Field Programmable Gate Array) or a reconfigurable processor whereconnections and settings of circuit cells within an LSI can bereconfigured is also possible.

Further, if integrated circuit technology comes out to replace LSI's asa result of the advancement of semiconductor technology or a derivativeother technology, it is naturally also possible to carry out functionblock integration using this technology. Application of biotechnology isalso possible.

In the above-mentioned embodiments, antennas have been described.However, the present invention is similarly applicable to an antennaport.

The antenna port refers to a theoretical antenna! made of one or aplurality of physical antennas. That is, the antenna port is notnecessarily limited to one physical antenna but may be an antenna arrayor the like made of a plurality of antennas.

For example, in the 3GPP LTE, how many physical antennas constitute theantenna port is not defined, but the antenna port is defined as aminimum unit in which the base station can transmit different referencesignals.

Further, the antenna port may be defined as a minimum unit formultiplying the weight of precoding vectors.

The disclosure of Japanese Patent Application No. 2009-031652, filed onFeb. 13, 2009, including the specification, drawings and abstract, isincorporated herein by reference in its entirety.

INDUSTRIAL APPLICABILITY

The communication apparatus and the communication method according tothe present invention can be applied to a mobile communication systemsuch as LTE-Advanced.

1. A communication apparatus comprising: a determination section thatdetermines a maximum value of the number of clusters such that themaximum value of the number of clusters to allocate to anothercommunication apparatus is reduced as the number of eodewords of atransmission signal to allocate to the other communication apparatusincreases; and a scheduling section that allocates a band of atransmission signal to be transmitted by the other communicationapparatus based on the determined maximum value of the number ofclusters.
 2. The communication apparatus according to claim 1, whereinthe determination section determines the number of clusters such that anamount of signaling is equal to or less than a reference number of bitsand is closest to a reference number of bits, as the maximum value ofthe number of clusters according to each number of codewords.
 3. Thecommunication apparatus according to claim 1, wherein the determinationsection reduces available start resource blocks or end resource blocksof clusters to allocate to the other communication apparatus as thenumber of codewords increases.
 4. A communication apparatus comprising:a band identifying section that determines that a maximum value of thenumber of clusters to allocate to the communication apparatus is smalleras the number of codewords allocated to the communication apparatus islarger, and identifies a transmission band allocated to thecommunication apparatus, based on the number of codewords and themaximum value of the number of clusters; and a transmission section thattransmits a data signal using the identified transmission band.
 5. Acommunication method comprising: determining a maximum value of thenumber of clusters such that the maximum value of the number of clustersto allocate to another communication apparatus is reduced as the numberof codewords of a transmission signal to allocate to the othercommunication apparatus increases; and performing allocation of a bandof a transmission signal to be transmitted by the other communicationapparatus, based on the determined maximum value of the number ofclusters.